1. Field of the Invention
The present invention relates to a calcium-carbonate-granule-containing dentifrice which permits tactile sensation of cleaning effects in the mouth, can be prepared at a low cost, is free from adsorption of a flavoring component and is excellent in the refreshed feeling after use.
2. Description of the Related Art
Various oral compositions blended with granules or granule-like materials have conventionally been known. For example, medicinal components such as medicaments and enzymes are incorporated in granules to exhibit their effects or to give an aesthetic appreciation to the products. Some granules are adjusted to have a size or strength perceivable in the mouth. Described specifically, granules are prepared so that they can be perceived immediately after toothbrushing is started but can no more be perceived along the toothbrushing process, whereby the cleaning degree of plaque can be found by the tactile sensation. Some granules are, on the other hand, prepared so that they cannot be perceived at all from the very beginning of the toothbrushing, but the cleaning effect can be confirmed only with the eyes.
As an oral composition containing granules, a granule-containing dentifrice available by binding the granules with an inorganic or organic binder is proposed (Japanese Patent Application Laid-Open No. 299211/1989, Japanese Patent Application Laid-Open No. Hei 243815/1992). In addition, an oral composition substantially free of an organic and/or inorganic binder and comprising an aggregate formed of at least two fine-grain materials different in particle size is proposed (Japanese Patent Application Laid-Open 506885/1998).
Also proposed is use of a special synthesizing method for preparing particles substantially free of a binder and having a specific particle size and shape (Japanese Patent Application Laid-Open No. 59716/1998).
The above-described compositions or process, however, is accompanied with such a problem as cumbersome preparation processor high production cost, because it needs addition of an organic or organic binder, aggregation or granulation of a mixture of at least two different materials, or a special synthesizing process. Moreover, a flavoring gent contained in a dentifrice is adsorbed to the granules owing to the organic or inorganic binder or the special shape of the granules formed as a result of the synthesis, which disturbs the dentifrice from exhibiting refreshed feeling. Furthermore, when granulation is conducted without using particles other than ordinarily-employed polishing particles having an average primary particle size of 1 to 20 xcexcm, it is difficult to control the particle size and crushing size.
An object of the present invention is therefore to provide a calcium-carbonate-granule-containing dentifrice which permits tactile sensation of cleaning effects in the mouth, can be prepared at a low cost, is free from al adsorption of a flavoring component and is excellent in the refreshed feeling after use.
Another object of the present invention is to provide a process for preparing the calcium carbonate granules and calcium carbonate granules prepared by the process.
Paying attention to the cohesive force of calcium carbonate particles having a markedly fine average primary particle size, the present inventors have found that incorporation of granules composed substantially singly of calcium carbonate in a dentifrice permits tactile sensation of the granules in the mouth and recognition of cleaning effects without giving almost no unpleasant feeling of foreign matters; enhances cleaning power without scratching tooth; and does not impair the refreshed feeling of the dentifrice.
In one aspect of the present invention, there is thus provided a dentifrice comprising granules which are composed substantially of calcium carbonates alone and which have an average granule size of 50 to 500 xcexcm and the crushing resistance of 1 to 20 g/granule, said granules being obtained by binding thereto calcium carbonate particles having an average primary particle size of 0.01 to 0.5 xcexcm.
In another aspect of the present invention, there is also provided a process for preparing calcium carbonate granules, which comprises granulating calcium carbonate particles of an average primary particle size of 0.01 to 0.5 xcexcm, which has been obtained by allowing a CO2 gas to pass through a calcium hydroxide suspension using a medium selected from a group consisting of calcium carbonate, calcium hydroxide and water, and then drying the resulting granules in a CO2-containing gas.
In a further aspect of the present invention, there is also provided a process for preparing calcium carbonate particles, which comprises introducing, to a suspension containing 1 to 20 wt. % of calcium hydroxide, a CO2-containing gas until a carbonating ratio reaches at least 90% but less than 100%, granulating the resulting suspension and then converting the resulting granules to calcium carbonate ones in a CO2-containing gas.
In a still further aspect of the present invention, there is also provided the above-described process for preparing calcium carbonate granules, wherein the calcium carbonate granules thus obtained have an average granule size of 50 to 500 xcexcm and crushing resistance of 1 to 20 g/granules.
The dentifrice according to the present invention permits tactile sensation of the granules in the mouth and recognition of their effects but hardly gives an unpleasant feel of foreign matters; has enhanced cleaning power without scratching tooth; and is excellent in refreshed feeling.
A process for preparing calcium carbonate granules is reduced in a production cost owing to the simplification of preparation steps and the granules obtained by this process are excellent as calcium carbonate granules for dentifrice.